Metabolic Issues

Thirty publications (15 cross-sectional, 10 prospective, and 5 experimental) were selected on the basis of relevance and quality of design and methods. Findings from large cross-sectional studies, in conjunction with those from well-powered prospective cohort studies with long periods of follow-up, show a positive association between greater intakes of SSBs and weight gain and obesity in both children and adults. Findings from short-term feeding trials in adults also support an induction of positive energy balance and weight gain by intake of sugar-sweetened sodas, but these trials are few.

A school-based intervention found significantly less soft-drink consumption and prevalence of obese and overweight children in the intervention group than in control subjects after 12 mo, and a recent 25-week randomized controlled trial in adolescents found further evidence linking SSB intake to body weight.

The weight of epidemiologic and experimental evidence indicates that a greater consumption of SSBs is associated with weight gain and obesity. Although more research is needed, sufficient evidence exists for public health strategies to discourage consumption of sugary drinks as part of a healthy lifestyle.

In a meta-analysis of 88 studies, we examined the association between soft drink consumption and nutrition and health outcomes. We found clear associations of soft drink intake with increased energy intake and body weight. Soft drink intake also was associated with lower intakes of milk, calcium, and other nutrients and with an increased risk of several medical problems (e.g., diabetes).

In the NHS and HPFS cohorts, the genetic association with BMI was stronger among participants with higher intake of sugar-sweetened beverages than among those with lower intake. In the combined cohorts, the increases in BMI per increment of 10 risk alleles were 1.00 for an intake of less than one serving per month, 1.12 for one to four servings per month, 1.38 for two to six servings per week, and 1.78 for one or more servings per day (P<0.001 for interaction).

For the same categories of intake, the relative risks of incident obesity per increment of 10 risk alleles were 1.19 (95% confidence interval [CI], 0.90 to 1.59), 1.67 (95% CI, 1.28 to 2.16), 1.58 (95% CI, 1.01 to 2.47), and 5.06 (95% CI, 1.66 to 15.5) (P=0.02 for interaction). In the WGHS cohort, the increases in BMI per increment of 10 risk alleles were 1.39, 1.64, 1.90, and 2.53 across the four categories of intake (P=0.001 for interaction); the relative risks for incident obesity were 1.40 (95% CI, 1.19 to 1.64), 1.50 (95% CI, 1.16 to 1.93), 1.54 (95% CI, 1.21 to 1.94), and 3.16 (95% CI, 2.03 to 4.92), respectively (P=0.007 for interaction).

CONCLUSIONS: The genetic association with adiposity appeared to be more pronounced with greater intake of sugar-sweetened beverages.

Children in the United States consume on average almost three times as many calories from sugar-sweetened beverages as the amount provided in our trial. We speculate that decreased consumption of such beverages might reduce the high prevalence of overweight in these children.

Dietary sugars, most of which are AS (added sugars), are a major contributor of calories in the diets of U.S. children. Only AS in non-dairy sources were associated with weight although the direction differed by the form consumed. AS in beverages were associated positively and those in foods were associated inversely with children's weight status.

Recent data show that SSB consumption has increased globally, thus putting many at risk for the onset of weight gain, T2DM, hypertension, CVD, and other chronic illnesses. The mechanisms whereby such diseases progress are closely linked to insulin resistance, pancreatic β-cell dysfunction, visceral adiposity, dyslipidemia, and inflammation. The current mini-review evaluated recent literature (past decade) and shows that SSB consumption worsens the risk for MetS, T2DM, and CVD onset. However, there are limitations; for example, many do not take the sex and/or ethnicity of participants into account, although it is evident that such factors may contribute to the complexity of the results.

The short-term nature of numerous studies is also a problem as long-term effects can therefore only be projected or predicted. Together these data highlight the need for (1) well-designed basic and clinical studies to obtain a clearer picture, (2) further research into the molecular mechanisms underlying the development of such debilitating conditions, and (3) increased roll-out of educational programs to inform the general public of the harmful effects of high SSB intake.

SSBs are the greatest contributor to added-sugar intake in the United States and are thought to promote weight gain in part because of incomplete compensation for liquid calories at subsequent meals. SSBs may also increase T2DM and cardiovascular risk independently of obesity as a potential contributor to a high dietary GL and increased fructose metabolism, leading to inflammation, insulin resistance, impaired β-cell function, and high blood pressure, as well as accumulation of visceral adiposity/ectopic fat and atherogenic dyslipidemia.

For these reasons and because they have little nutritional value, intake of SSBs should be limited, and SSBs should be replaced by healthy alternatives such as water.

Dietary sugar and body weight: have we reached a crisis in the epidemic of obesity and diabetes?: health be damned! Pour on the sugar. (2014) Bray GA, Popkin BM.

Meta-analyses and randomized clinical trials were used to evaluate outcomes of beverage and fructose intake. About 75% of all foods and beverages contain added sugar in a large array of forms. Consumption of soft drinks has increased fivefold since 1950. Meta-analyses suggest that consumption of sugar-sweetened beverages (SSBs) is related to the risk of diabetes, the metabolic syndrome, and cardiovascular disease.

Drinking two 16-ounce SSBs per day for 6 months induced features of the metabolic syndrome and fatty liver. Randomized controlled trials in children and adults lasting 6 months to 2 years have shown that lowering the intake of soft drinks reduced weight gain. Recent studies suggest a gene-SSB potential relationship. Consumption of calorie-sweetened beverages has continued to increase and plays a role in the epidemic of obesity, the metabolic syndrome, and fatty liver disease. Reducing intake of soft drinks is associated with less weight gain.

Taken together, these various results demonstrate unequivocally that sucrose consumed in a drink reduces subsequent energy intake. This effect, however, is not sufficient to prevent increased cumulative energy intake, even when measured using a parallel-groups design (non-significant increase of 58 kcal), and optimising the timing of the test-meal interval to coincide with the peak effect of the preload on blood glucose concentration.

SSBs and NON-ALCOHOLIC LIVER DISEASE

Long term nutritional intake and the risk for non-alcoholic fatty liver disease (NAFLD): A population based study (2007)

Background/Aims

Weight loss is considered therapeutic for patients with NAFLD. However, there is no epidemiological evidence that dietary habits are associated with NAFLD. Dietary patterns associated with primary NAFLD were investigated.

Methods

A cross-sectional study of a sub-sample (n = 375) of the Israeli National Health and Nutrition Survey. Exclusion criteria were any known etiology for secondary NAFLD. Participants underwent an abdominal ultrasound, biochemical tests, dietary and anthropometric evaluations. A semi-quantitative food-frequency questionnaire was administered.

NAFLD patients have a higher intake of soft drinks and meat and a tendency towards a lower intake of fish rich in omega-3. Moreover, a higher intake of soft drinks and meat is associated with an increased risk of NAFLD, independently of age, gender, BMI and total calories.

While the rise in non-alcoholic fatty liver disease (NAFLD) parallels the increase in obesity and diabetes, a significant increase in dietary fructose consumption in industrialized countries has also occurred. The increased consumption of high fructose corn syrup, primarily in the form of soft-drinks, is linked with complications of the insulin resistance syndrome. Furthermore, the hepatic metabolism of fructose favors de novo lipogenesis and ATP depletion. We hypothesize that increased fructose consumption contributes to the development of NAFLD.

METHODS: A dietary history and paired serum and liver tissue were obtained from patients with evidence of biopsy-proven NAFLD (n=49) without cirrhosis and controls (n=24) matched for gender, age (± 5 years), and body mass index (± 3 points).

RESULTS: Consumption of fructose in patients with NAFLD was nearly 2-3 fold higher than controls [365 kcal. vs 170 kcal (p<0.05)]. In patients with NAFLD (n=6), hepatic mRNA expression of fructokinase (KHK), an important enzyme for fructose metabolism, and fatty acid synthase, an important enzyme for lipogenesis were increased (p=0.04 and p=0.02 respectively). In an AML hepatocyte cell line, fructose resulted in dose-dependent increase in KHK protein and activity.

CONCLUSION: The pathogenic mechanism underlying the development of NAFLD may be associated with excessive dietary fructose consumption.

BACKGROUND: Little is known about dietary habits and their relationships with liver disease in nonalcoholic fatty liver disease (NAFLD) patients, particularly in the absence of obesity, diabetes or hyperlipidemia.

OBJECTIVE: To assess the association between soft drink consumption and the presence of fatty liver in NAFLD patients who do not have classic risk factors.

METHODS: Three hundred ten patients with NAFLD diagnosed by ultrasound were assessed for 36 months in a cross-sectional manner. Thirty-one patients (10%) who had NAFLD without classic risk factors were compared with 30 healthy controls. Physical activity was assessed during the preceding week and year, and every six months for 36 months. Data on daily dietary intake of food and soft drink, and the source of added sugar were collected during two seven-day periods, at the beginning of the study, and within two weeks after the metabolic tests by using a validated food questionnaire given by a trained dietician. Insulin resistance and lipid peroxidation were assessed by homeostasis model assessment-insulin resistance index (HOMA-IRI) and malondialdehyde (MDA) levels, respectively.

RESULTS: Eighty per cent of patients (25 of 31) consumed an excessive amount of soft drink beverages (more than 50 g/day of added sugar) for 36 months, compared with 20% in healthy controls (P<0.001). Twenty per cent of patients consumed one drink per day, 40% consumed two to three drinks per day, and 40% consumed more than four drinks per day for most days during 36 months. The most common soft drinks consumed were regular Coca-Cola (40% of patients), Diet Coke (40%) and flavoured fruit juices (20%). Ultrasound findings revealed mild fatty liver in 44% of cases (n=14), moderate fatty liver in 38% (n=12), and severe fatty liver in 18% (n=5). HOMA-IRI and MDA levels were significantly higher in patients with NAFLD than in healthy controls (HOMA-IRI, 3.7 versus 1.7, P<0.001; and MDA, 420±300 μmol/mL versus 200±100 μmol/mL; P<0.001). When controlled for other factors, including dietary composition and physical activity, soft drink beverage consumption was the only independent variable that was able to predict the presence of fatty liver in 82.5% of cases with a sensitivity of 100%, a specificity of 76%, a positive predictive value of 57% and a negative predictive value of 100%.

CONCLUSION: The present study may add important insight into the role of sugar-sweetened beverage consumption as a cause of fatty liver in patients without risk factors. Patients are encouraged to change their long-standing drinking behaviour.

Are SSBs Addictive or Habit Forming?

Using scanner data, we estimated demand for nine nonalcoholic beverages under habit formation. We found strong evidence for habit formation. Although demand for sugar-sweetened beverages by low-income households is less elastic to own-price changes compared with high-income households, there is evidence that high-income households consider beverages to be more substitutable than low-income households do. A half-cent per ounce tax on store-purchased sugar-sweetened beverages will result in a moderate reduction in consumption of sugar-sweetened beverages for both income strata. Because of habit formation, long-run national tax revenue from a sugar-sweetened beverage tax is about 15 to 20% lower than short-run revenue.

Conclusions. From legal and administrative perspectives, a federal junk food tax appears feasible based on product categories or combination category-plus-nutrient approaches, using a manufacturer excise tax, with additional support for sugar and graduated tax strategies.

Study question: What has been the effect on purchases of beverages from stores in Mexico one year after implementation of the excise tax on sugar sweetened beverages?

Methods: In this observational study the authors used data on the purchase of beverages in Mexico from January 2012 to December 2014 from an unbalanced panel of 6253 households providing 205 112 observations in 53 cities with more than 50 000 inhabitants. To test whether the post-tax trend in purchases was significantly different from the pretax trend, the authors used a difference in difference fixed effects model, which adjusts for both macroeconomic variables that can affect the purchase of beverages over time, and pre-existing trends. The variables used in the analysis included demographic information on household composition (age and sex of household members) and socioeconomic status (low, middle, and high). The authors compared the predicted volumes (mL/capita/day) of taxed and untaxed beverages purchased in 2014—the observed post-tax period—with the estimated volumes that would have been purchased if the tax had not been implemented (counterfactual) based on pretax trends.

Study answer and limitations: Relative to the counterfactual in 2014, purchases of taxed beverages decreased by an average of 6% (−12 mL/capita/day), and decreased at an increasing rate up to a 12% decline by December 2014. All three socioeconomic groups reduced purchases of taxed beverages, but reductions were higher among the households of low socioeconomic status, averaging a 9% decline during 2014, and up to a 17% decrease by December 2014 compared with pretax trends. Purchases of untaxed beverages were 4% (36 mL/capita/day) higher than the counterfactual, mainly driven by an increase in purchases of bottled plain water.

What this study adds: The tax on sugar sweetened beverages was associated with reductions in purchases of taxed beverages and increases in purchases of untaxed beverages. Continued monitoring is needed to understand purchases longer term, potential substitutions, and health implications.

Objective: To estimate changes in sales of sugar sweetened beverages (SSB) and plain water after a 1 peso per liter excise SSB tax was implemented in Mexico in January 2014.

Material and Methods: We used sales data from the Monthly Surveys of the Manufacturing Industry from January 2007 to December 2015. We estimated Ordinary Least Squares models to assess changes in per capita sales of SSB and plain water adjusting for seasonality and the global indicator of economic activity.

Results: We found a decrease of 7.3% in per capita sales of SSB and an increase of 5.2% of per capita sales of plain water in 2014–2015 compared to the pre-tax period (2007–2013).

Conclusions: Adjusting for variables that change over time and that are associated with the demand for SSB, we found the tax was associated with a reduction in per capita sales of SSB. The effectiveness of the tax should be evaluated in the medium and long term.

American Public Health Association: Taxes on Sugar-Sweetened Beverages (2012)

Proposed Recommendations Statement

In order to raise significant funds for obesity prevention and to reduce the consumption of sugar-sweetened beverages, the American Public Health Association should support federal, state, and local governments in enacting excise taxes, which would raise the average price of all sugar-sweetened beverages. The most commonly proposed tax amount, a penny per ounce, would raise the price approximately 20%. Such a tax could raise more than $13 billion in 2012 in all states combined and a significant amount of revenue in each individual state. For example, in California, a tax at that level could raise more than $1.1 billion per year; in Mississippi, more than $136 million; in Massachusetts, close to $280 million; and, in Nebraska, almost $100 million. The tax should be passed on to consumers, and revenue raised should be dedicated to a variety of evidence-based child and adult obesity prevention programs. APHA recommends that, in writing statutes, jurisdictions use the model language set forth by ChangeLab Solutions.

Research has shown that sugar-sweetened beverages are price elastic: it is estimated that every 10% increase in price would decrease consumption by 10%.26 A recent study revealed that a penny-per-ounce tax would reduce consumption by 15% among adults 25–64 years of age and prevent 2.4 million diabetes person-years, 95,000 coronary heart events, 8,000 strokes, and 26,000 premature deaths. It would avoid more than $17 billion in total medical costs.27 Research also shows a beneficial effect of a soda tax on body mass index (BMI) in overweight and low-income children. However, a reduction in consumption is likely only if consumers are aware of the price increase before they purchase the product, making an excise tax preferable to a sales tax. An excise tax would be levied on the beverage manufacturer, which would pass the cost on to consumers, resulting in a higher shelf price. A price increase through sales tax would be noted only by a vigilant customer who reads the register receipt after purchasing the product.